Process and device for producing a plastic layer of high optical quality

ABSTRACT

A process for the continuous production of a plastic sheet of high optical quality capable of being used in laminated glasses, having at least a thin layer resistant to scoring and abrasion which entails high-speed centrifugal spraying of a mixture of reaction components, onto a plane horizontal support carried in a uniform movement of advancement relative to the spraying.

This application is a continuation, of application Ser. No. 729,573,filed May 2, 1985, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the production of a transparent plasticsheet of high optical quality having at least a layer exhibiting scoringresistance and abrasion resistance.

2. Description of the Background

Laminated safety glasses, used particularly as vehicle windshields,having a transparent rigid support of silicate glass, a plastic layerhaving energy-absorbing properties (EA layer) and a coating plasticlayer having surface properties particularly of resistance to scoring orscratching and abrasion, called the inside protective layer (IP layer),have been described in French Pat. Nos. 2,134,255, 2,398,606, and alsoin European Pat. No. 0,054,491. The coating layer having the surfaceproperties used in these laminated glasses is, for example, thatdescribed in French Pat. Nos. 2,187,719 and 2,251,608. This layer,referred to as self-healing, from which surface impressionsspontaneously disappear after a short lapse of time, has, under normaltemperature conditions, a high elastic deformation capacity, a slightmodulus of elasticity, less than 2000 daN/cm2, and preferably less than200 daN/cm2, and an elongation at break of more than 60% with less than2% plastic deformation and preferably an elongation at break of morethan 100% with less than 1% plastic deformation. Preferred layers ofthis type are thermosetting polyurethanes having a modulus of elasticityof about 25 to 200 daN/cm2 and an elongation of about 100 to 200% withless than 1% plastic deformation.

To produce the laminated glasses described above, a two-layer sheet isgenerally previously prepared by first, forming a thermosettingpolyurethane layer by casting of the reaction mixture of the componentson a casting support, and then polymerizing the monomers and forming athermosetting layer with a thickness that can vary from 0.1 to 0.8 mmand forming on the first layer the second layer having energy-absorbingproperties by casting of the reaction mixture of components or also byextrusion of a suitable resin that is already polymerized.

The reactive layer without solvent used to produce the thermosettingpolyurethane layer requires, in order obtain a high optical quality, theproduction of a layer with a thickness greater than 0.1 mm andpreferably greater than 0.2 mm.

It has been found that a thinner layer of the order of some dozens ofmicrons could still attain the required surface properties such asresistance to scoring and resistance to abrasion when this layer is usedto coat another soft layer, as is the case for the laminated glassesdescribed above where said layer with the surface properties is used tocoat the EA layer.

Moreover, the production of such a thin layer would seem to be besteffected by spraying with a spray gun inasmuch as this technique candeposit small amounts of deposited material. Unfortunately, sprayingwith a spray gun to form a thin layer is not a satisfactory technique aslayers so produced are not of homogeneous thickness nor is the opticalquality good. In particular, the optical quality is found to suffer fromorange peel. This is believed to be due to the viscosity differentialbetween the components forming the mixture to be sprayed. Although someattempts have been made to alleviate such drawbacks by using particularsolvents or mixtures of solvents. However, these attempts have provenunsuccessful inasmuch as other problems arise from solvent evaporation.

Thus, a need continues to exist for a process for the continuousproduction of a plastic sheet which can be used in laminated glasses,said sheet having at least a thin layer of high optical quality and alsohaving excellent resistance to scoring and abrasion.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide aprocess for the continuous production of a plastic sheet having highoptical quality which can be used in laminated glasses, said sheethaving at least a thin layer of high optical quality.

It is also an object of this invention to provide a process for thecontinuous production of a plastic sheet having high optical qualitywhich can be used in laminated glasses, said sheet having also excellentresistance to scoring and abrasion.

Moreover, it is also an object of the present invention to provide adevice for the continuous production of a plastic sheet of high opticalquality capable of being used in laminated glasses, which has highoptical quality and excellent resistance to scoring and abrasion.

According to the present invention, the foregoing and other objects areattained by providing a process for the continuous production of aplastic sheet of high optical quality capable of being used in laminatedglasses, having at least a thin layer resistant to scoring and abrasion,which entails high-speed centrifugal spraying of a mixture of reactioncomponents onto a plane horizontal support which is carried in a uniformmovement of advancement relative to the spraying.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood from the following detailed descriptions when considered inconnection with the accompanying drawing(s) in which like referencecharacters designate like or corresponding parts and wherein:

FIG. 1 illustrates a line for producing a layer of high optical qualityby spraying according to the present invention.

FIG. 2 shows, in section, a spray head.

FIG. 3 illustrates a line for producing a two-layer sheet used inlaminated glasses.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a process for the continuous productionof a plastic sheet which can be used advantageously in laminatedglasses. The plastic sheet has at least a thin layer of material of highoptical quality.

According to the present invention, this layer is obtained by high-speedspraying of a mixture of reaction components on a horizontal planesupport carried in an advancement movement that is uniform relative tothe spraying, followed by a treatment assuring polymerization of thelayer.

The centrifugal spraying used according to the invention isadvantageously performed with a spray head such as a bowl revolving at aspeed between about 1000 and 80,000 rpm.

According to one aspect of the invention, the plastic sheet isessentially formed by the layer obtained by spraying. For this purpose,a continuous horizontal plane support is used whose surface partiallyadheres to the material able to form the layer so that the movement ofthe support causes carrying of the material. The support is given arelative uniform advancement movement and the mixture of reactioncomponents is sprayed on the support by high-speed centrifugal spraying.Then, the formed layer is polymerized and removed from the support.

According to another aspect of the invention, several successive layersare formed in the same way by centrifugal spraying of the same reactionmixture or different reaction mixtures, in the first case to increasethe thickness of said sheet and to improve its mechanical properties or,in the second case, to form a composite sheet with the desiredproperties.

Under an advantageous aspect of the invention, the layer obtained bycentrifugal spraying is an inside protective layer (IP layer), which atthe moment of its production is associated with a plastic layer havingdifferent properties, for example, a layer having energy-absorbingproperties (EA layer). Thus a two-layer sheet is prepared which can beused directly for the production of safety glasses of the type describedabove. To make such a two-layer glass, it is possible first to form theIP layers by centrifugal spraying, then the EA layer by reactive castingas described below or in a variant the reactive spraying or, inversely,the layer having energy-absorbing properties is formed first, then theIP layer.

Preferably to avoid premature polymerization, the mixing is performeddirectly in the spray head.

When the layer is formed by spraying directly on the support, theadherence of the sprayed material to the support surface should not betoo high, otherwise the layer formed after polymerization cannot bedetached from the support or also runs the risk of being altered duringdetachment. Thus, depending on the nature of the sprayed material andalso that of the support, the surface of this latter can be previouslytreated with separation agents when the adherence is too strong. Asseparation agents, it is possible to use stearates, silicones,fluorohydrocarbons, paraffin, waxes, an addition product of ethyleneoxide such as described, for example, in French Pat. No. 2,383,000.These same products or other suitable products can also be used when thecasting support is plastic, metal, etc.

Treatment of the support surface can be done by wetting this surfacewith a liquid composition comprising the separation agent, followed byan evaporation of the liquid phase. Various processes can be used toapply the treating composition to the support surface. It is possible,for example, to proceed by streaming, spraying, etc.

Under another advantageous aspect of the invention, when the reactionmixture is able to polymerize under the action of heat, spreading of thelayer being formed can be improved by performing the spraying when thesupport to be coated is hot. Thus, when it is a question of forming athermosetting polyurethane layer as described below, the best spreadingis obtained when the support temperature is between about 25° C. and 60°C.

The reaction mixture used for spraying according to the invention is amixture of two components able to form a polyurethane layer,particularly a self-healing polyurethane layer having such surfaceproperties as resistance to scoring and abrasion.

Examples of monomers that are suitable for the preparation of thesepolyurethanes, on the one hand, are aliphatic difunctional isocyanatessuch as 1,6-hexanediisocyanate, 2,2,4-trimethyl-1,6-hexanediisocyanate,2,2,4-trimethyl-1,6-hexanediisocyanate,1,3-bis(isocyanatomethyl)benzene, bis(4isocyanatocyclohexyl)methane,bis(3-methyl-4-isocyanatocyclohexyl)methane,2,2-bis(4-isocyanatocyclohexyl)propane and3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate as well asbiurets, isocyanurates and prepolymers of these compounds having afunctionality of 3 or more and, on the other hand, polyfunctionalpolyols, such as branched polyols such as polyesterpolyols andpolyetherpolyols obtained by reaction of polyfunctional alcohols,particularly 1,2,3-propanetriol (glycerol),2,2-bis(hydroxymethyl)-1-propanol (trimethylolethane),2,2-bis(hydroxymethyl)-1-butanediol (trimethylolpropane),1,2,4-butanediol, 1,2,6-hexanetriol,2,2-bis(hydroxymethyl)-1,3-propanediol (pentaerythritol) and1,2,3,4,5,6-hexanehexol (sorbitol), with aliphatic diacids, such asmalonic acid, succinic acid, glutaric acid, adipic acid, suberic acidand sebacic acid or with cyclic ethers, such as ethylene oxide,1,2-propylene oxide and tetrahydrofuran, or also polycaprolactonepolyols. As the polyol component, it is also possible to use a mixtureof at least a long diol such as polyesterdiol or a polyetherdiol with amolecular mass between 500 and 4000, and at least a short diol and, ifnecessary, at least a polyol with a functionality equal to or greaterthan three.

When it is desired to obtain a coating layer having improved moistureresistance properties, there can be used as the polyol component aplurifunctional polyol exhibiting ethoxy-propoxy chains, particularly adifunctional polyol comprising 5 to 17% by weight of OH radicals, withan average molecular weight between about 200 and 600 and comprisingabout 80% by weight of ethoxy radicals in the ethoxy-propoxy chain. Thisdifunctional polyol goes into the polyol-isocyanate mixture at a rate ofabout 25 to 70% by weight of said mixture. The plurifunctional polyolcan also be a polyol with a functionality greater than 2 comprisingabout 0.4 to 14% by weight of OH radicals, with an average molecularweight between about 500 and 15,000 and comprising about 50 to 90% byweight of ethoxy radicals in the ethoxy-propoxy chains. This polyol goesinto the polyol-isocyanate mixture at a rate of about 30 to 90% byweight of said mixture. The trifunctional polyol is preferably apolyetherpolyol with a base of trimethylolpropane or glycerol orpropylene oxide, or a lactonepolyesterpolyol with a base oftrimethylolpropane or glycerol or caprolactone. The polyfunctionalpolyol can also be a tetrafunctional polyol comprising 0.7 to 14% byweight of OH radicals, with an average molecular weight between about500 and 10,000 and comprising about 10 to 80% by weight of ethoxyradicals in the ethoxy-propoxy chains.

High-speed centrifugal spraying according to the invention makes itpossible to obtain a homogeneous reaction mixture from components withvery different viscosities.

As a variant, the centrifugal spraying can be an electrostatic sprayingknown in the art, with the centrifugal spraying being performed in anelectric field.

When a two-layer sheet is produced according to the invention, one bycentrifugal spraying to form the IP layer, the other by reactive castingto form the EA layer, this second layer is formed by reactive casting ofa reaction mixture of an isocyanate component and a component withactive hydrogens, particularly a polyol component. If necessary, thesecond layer can be produced before the first IP layer. The isocyanatecomponent entails at least an aliphatic, cycloaliphatic diisocyanate ora diisocyanate prepolymer, this component having a viscosity less thanabout 5000 centipoises, at +40° C., the polyol component comprising atleast a difunctional long polyol with a molecular mass between 500 and4000 and at least a short diol as a chain-lengthening agent. By reactivecasting is meant casting in the form of a layer or film of a liquidmixture of the components as monomers or prepolymers, followed by apolymerization of this mixture by heat. This reactive casting whichprovides the layer with good mechanical and optical properties will bedescribed more completely in the description below.

The proportions of the polyurethane components are selected preferablyto obtain a stoichiometrically balanced system, i.e., the ratio of theNCO equivalent groups, which are contributed by the diisocyanatecomponent, to the OH equivalent groups, which are contributed by thepolyol component, i.e., the long polyol or polyols and the short polyolor polyols, is on the order of 1. When the NCO/OH ratio is less than 1,and the more it decreases, the faster the mechanical properties desiredfor the application become unsatisfactory. When the NCO/OH ratio isgreater than 1, and the more it increases, the more certain mechanicalproperties of the layer obtained by reactive casting can be enhanced,for example, the layer becomes stiffer. Yet, given the higher cost ofthe ioscyanate component in comparison with that of the glycolcomponent, the choice of these NCO/OH ratios as approximately equal to 1is a good compromise between the properties obtained and the cost.

The proportions between the long polyol and the short polyol can vary asa function of the desired properties and also of the ratio of theequivalent groups, the number of OH equivalent groups of the short diol,however, generally representing 20 to 70% of the total equivalent groupsof the mixture forming the polyol component in the case where the ratioof NCO equivalent groups to the OH groups is on the order of 1. When theproportion of short diol increases, the layer hardens and its modulusgenerally increases. Suitable diisocyanates used within the context ofthe invention are from the following aliphatic difunctional isocyanates:hexamethylenediisocyanate (HMDI), 2,2,4-trimethyl-6-hexanediisocyanate(TMDI), bis-4-isocyanatocyclohexylmethane (Hylene W),bis-3-methyl-4-isocyanatocyclohexylmethane,2,2-bis(4-isocyanatocycloclohexyl)propane,3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI),m-xylylenediisocyoanate (XDI), m- and p-tetramethylxylylenediisocyanate(m- and p-TMXDI), transcyclohexane-1,4-diisocyanate (CHDI),1,3-(diisocyanatomethyl)cyclohexane (hydrogenated XDI). Preferably IPDIis used, particularly for reasons of cost.

Advantageously, an isocyanate component containing urea functions isused. The urea functions improve certain mechanical properties of thelayer. The urea proportion can represent up to about 10% of the totalweight of the isocyanate component with urea functions. Preferably theurea proportion is between 5 and 7% of the total weight of saidcomponent. For the reason mentioned above,3-isocyanatomethyl-3,5,5-trimethylcyclohexyldiisocyanate comprising ureafunctions (IPDI and derivatives) is used. Suitable long polyols areselected from polyetherdiols or polyesterdiols with a molecular mass of500-4000; the polyesterdiols being products of esterification of adiacid such as adipic, succinic, palmitic, azelaic, sebacic, ophthalicacid and a diol such as an ethylene glycol, 1,3-propanediol,1,4-butanediol, 1,6-hexandiol, or polyetherdiols that have the generalformula with n=2 to 6; and m such that the molecular mass is located inthe interval of 500-4000, or the poletherdiols of the general formulaH--[--(CH₂)_(n) ]_(m) OH, wherein n is 2 to 6, and m is such that themolecular weight is between about 500-4000. It is also possible to usepolyetherdiols having the formula: ##STR1## wherein m has a molecularweight between about 500-4,000. It is also possible to usepolycaprolactone diols.

A polytetramethylene glycol (n=4) with a molecular mass of 1000 ispreferably used.

Suitable chain-lengthening agents are short diols with a molecular massless than about 300 and preferably less than 150 such as: ethyleneglycol, 1,2-propanediol, 1,3-propanediol, 1,2-, 1,3- 1,4-propanediol,2,2-dimethyl, 1,3-propanediol (neopentylglycol), 1,5-pentanediol,1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol,cyclohexanedimethanol, bisphenol A, 2-methyl-2,4-pentanediol,3-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol,2,2,4-trimethyl-1,3-pentanediol, diethylene glycol, triethylene glycol,tetraethylene glycol, 2-butyne-1,4-diol, 1,4-butenediol and decanediolsubstituted and/or etherified, hydroquinone-bishydroxyethylether,bisphenol A etherified by two or more groups of propylene oxide,dimethylolpropionic acid. In general, the shorter the diol, the harderthe layer.

Preferably 1,4-butanediol is used which is a good compromise to obtain alayer that is neither too hard nor too soft, which is desired for thistype of application as an energy absorber.

The reactive casting implies a fast reaction for the layer to be formedin times compatible with industrial production. This requires a hightemperature, on the order of about 100° to 140° C., a temperature aswhich secondary branching reactions occur, creating, for example,allophanate and/or biuret groups between the urethane chains. ##STR2##

Under these operating conditions, even with difunctional components,when the NCO/OH ratio is approximately equal to 1, the resulting productis not completely thermoplastic; actually it is infusible and insolublein most of the solvents of polyurethanes such as tetrahydrofuran, anddimethylformamide. Advantage is taken of the improved mechanicalproperties with an equal formulation in relation to an equivalent systempolymerized at lower temperature where only a linear polycondensationoccurs.

When the NCO/OH ratio is less than 1 and on the order of 0.8 to 0.9, across-linking of the type described above occurs only in aninsignificant way.

In an embodiment of the polyurethane layer having energy-absorbingproperties, the polyol component can contain a slight proportion of atleast a polyol with a functionality equal to or greater than three andmonomeric aliphatic triols such as glycerol, trimethylolpropane, triolswith polyether chains, polycaprolactone triols, the molecular mass ofthese triols generally being between 90 and 1000. The addition of atriol causes additional bridge bonds between the polyurethane chains andcan thus further improve the cohesion of the layer.

The proportions between the long polyol, short diol and optionally thetriol can vary, depending on the properties desired. Generallyproportions are selected so that for a hydroxyl equivalent the longpolyol represents about 0.35 to 0.45 equivalent, the short diol about0.2 to 0.7 equivalent and the triol about 0 to 0.3 equivalent. Underthese conditions, the layer exhibits the following mechanicalcharacteristics, measured per standards AFNOR/NFT 46 002, 51 034, 54108.

stress at flow threshold at -20° C. less than or equal to 3 daN/mm2

stress at break R at +40° C. greater than or equal to 2 daN/mm2

elongation at break R at +20° C. between 250 and 400%

resistance to started tear Ra at +20° C. greater than or equal to 8.8daN/mm thickness.

The product can also be made by replacing a part of the polyol componentwith a product having various active hydrogens, such as an amine.

According to one aspect of the invention, a two-layer sheet is made,namely, an inside protective layer with a thickness of about 200 μm anda fine layer, for example on the order of 50 μm thick, essentiallyhaving adhesion properties. In this case, the inside protective layer ispreferably obtained by reactive casting of the mixture of components,whereas the adhesive layer is obtained by centrifugal spraying of thereaction mixture described above to form the EA layer.

Under another aspect of the invention, a two-layer sheet, one an insideprotective sheet, the other having energy-absorbing properties, isproduced by centrifugal spraying of reaction mixtures suitable for eachof the layers. If necessary, depending on the desired thicknesses, eachof these two layers can be made by a superposition of several layerswhich can be called elementary layers each corresponding to acentrifugal spraying.

The support for forming the layer or sheet on which the spraying orsprayings according to the invention are performed can be a rigid glassor metal support. It can also be a flexible support stretchedhorizontally as described, for example, in the publication of EuropeanPat. No. 0,038,760.

Under another aspect of the invention, the horizontal plane support onwhich the high-speed centrifugal spraying is performed is a stretchedflexible support that can be used as one of the elements going into thecomposition of a multilayer sheet, which can be used as it is or bybeing associated with other elements.

Thus, according to the invention a composite sheet can be producedcomprising a sheet of polyester, for example, particularly of ethyleneglycol polyterephthalate, coated with a layer of self-healingpolyurethane having such surface properties as resistance to scoring andabrasion, this layer being obtained by centrifugal spraying as indicatedabove.

For using this production, the process and means described in thepublication of European Pat. No. 0,038,760, already cited, willadvantageously be used.

As a variant, the stretched flexible support can be coated on these twofaces with a layer obtained by centrifugal spraying of a reactionmixture or of different mixtures. For this purpose, a first layer isformed on the support and after polymerization the coated support isturned over and another layer is formed on the face not coated by thefirst layer.

The invention also relates to a device constituting a line forproduction of at least a layer of high optical quality, by centrifugalspraying of a mixture of reaction components on a support from which itcan be detached or, if necessary, on a support going into thecomposition of a composite sheet.

The production line is divided into several zones, a support treatmentzone, a spraying zone and a zone for polymerization of the materialsupplied by spraying, and, if necessary, zones for forming a secondlayer, particularly by reactive casting of a mixture of the components.The production line according to the invention comprises a mobile planesupport, particularly of glass, a means to treat its surface with aseparation agent, at least a high-speed sprayer with revolving head, anda means for polymerization of the formed layer, the entire unitadvantageously being placed in a long enclosure divided intocompartments corresponding to the various zones. When it is used forproduction of a two-layer sheet, the device can further comprise thenecessary means for producing the second layer, said means being able tobe a casting head with a wide thin slit as described in French Pat. No.2,347,170, and a means for polymerizing this second layer, theseadditional means being placed downstream or upstream from the means forforming the layer by centrifugal spraying, depending on whether thelayer is formed by centrifugal spraying in the first or second place.

When the support goes into the composition of a composite sheet asindicated above, the production line will advantageously comprise themeans described in the publication of European Pat. No. 0,038,760already cited.

The production line shown in FIG. 1 consists of a long enclosure 1 cutinto compartments, passed through by a plane support 2 for forming thelayer, the layer, for example, being a continuous strip of a successionof glass plates placed side by side, and being carried at a uniformspeed by a roller conveyer 3. First, compartment 4 is equipped with ameans, for the pre-treatment of the glass ribbon with a separationagent. Spray gun 5 may be used for this purpose. This compartment isalso equipped with heating means 6 such as resistors to bring glassribbon 2 to the suitable temperature.

Next compartment 7 corresponds to the zone in which the layer is formedby centrifugal spraying. This compartment is equipped with a centrifugalspray means whose head 9 comprises a bowl revolving at high speed asdescribed below. Compartment 10 placed downstream corresponds to thepolymerization zone and consequently comprises means for assuring thepolymerization of the layer obtained by spraying, these means, ifnecessary, being heating means 11 such as resistors. Downstream from thepolymerization, means 12 are provided to detach layer 101 from theforming support and to wind it on reel 13.

At different places over its entire length, the line comprises means 14to eliminate static electricity in the environment of the glass ribbonbefore coating. These means can be electrostatic rods known in the art.

The line can also comprise cleaning means (not shown) to eliminate dustsand other particles deposited on the glass ribbon or film.

Head 9 of the high-speed centrifugal spray device shown in FIG. 2comprises a mobile part 15 consisting of revolving bowl 16 itself, solidwith a chuck 17 carrying a plate 18 and a stationary part 19 pierced bytwo feed pipes 20, 21 for the components, these pipes coming out in thecentral part of the plate.

To increase the length of travel to mix the two components introduced bypipes 20, 21 and also to improve this mixing before spraying, the bowl,on the one hand, exhibits an inside surface 22 whose generatrix isundulated, and plate 18, on the other hand, carries unevennesses or ribs23 directed upward, forming baffles.

FIG. 3 shows a line for producing a two-layer sheet, the first layerbeing the layer described above, the second layer being a layer havingenergy- absorbing properties so that said sheet can be used directly inthe production of the laminated glasses described above. This lineconsists of a long enclosure 26 cut into compartments, passed through bya plane support 27, for the formation of sheet 28, this support, likethe device described above, being a succession of glass plates placedside by side, and being carried at uniform speed by a roller conveyer29. The beginning of the line is identical with that described inconnection with FIG. 1, i.e., it comprises particularly a firstcompartment 30 for previous treatment of the glass ribbon with aseparation agent, a second compartment 31 corresponding to the zone forforming first layer 32 by centrifugal spraying, followed by acompartment 33 for polymerization of the formed layer. The line isfurther extended by compartments corresponding to the formation ofsecond plastic layer 34 by reactive casting of a mixture of components.The first, 35, of these compartments is equipped with a casting head 36with a wide thin slit 37 which serves for casting, in a regular andcontrolled way, liquid material 38 suitable for forming second layer 34.A suitable control head is, for example, that described in French Pat.No. 2,347,170. Downstream compartment 39 is equipped with means 40 forpolymerization of this second layer. Means 41 are placed at the end ofthe production line to remove the two-layer sheet from the glass ribbonand wind it on reel 42.

Electrostatic rods 43 and cleaning means (not shown) are also providedat several places in the line to eliminate dust and other particles.

The present invention will now be further illustrated by certainexamples and references which are provided for purposes of illustrationonly and are not intended to limit the present invention.

EXAMPLE 1

In this example a layer of high optical quality is formed by using thedevice described in connection with FIG. 1.

Continuously passing mobile glass support 2 is coated during its passagein compartment 4 with a separation agent which, for example, can be thatdescribed in French Pat. No. 2,383,000, namely, a modified ethyleneoxide product. In next compartment 7 the treated support receives acentrifugal spraying of a mixture of components with the followingproportions:

1000 g of a polyether with a molecular weight of about 450 obtained bycondensation of 1,2-propylene oxide with2,2-bis(hydroxymethyl)-1-butanol and having a free hydroxyl radicalcontent of about 10.5 to 12%, containing 1% by weight of a stabilizer,0.05% weight of a catalyst, namely, dibutyltin dilaurate and 0.1% byweight of a spreading agent,

1020 g of a 1,6-hexanediisocyanate biuret having a free isocyanateradical content of about 23.2%.

The polyol component exhibits a viscosity of about 620 centipoises at25° C. while the isocyanate component exhibits a viscosity of about 2300centipoises.

Centrifugal spraying is performed while the reaction mixture is at about25° C., with a bowl revolving at a speed of about 20,000 rpm, thediameter of the bowl being about 90 mm. Thus, a polyurethane layer ofabout 100 μm is formed, which is directed into the polymerization tunnelwhere it is polymerized by being brought to a temperature of about 100°C. for about 20 min.

The layer is removed from the glass ribbon by suitable means at the endof the line. It exhibits an excellent optical quality.

EXAMPLE 2

In this example a high-quality two-layer sheet is formed by using thedevice described in connection with FIG. 3.

The operation is the same as in example 1 for the formation of the firstpolyurethane layer, except its thickness is reduced to about 50 μm.

After polymerization of this layer, there is cast with a casting head asdescribed in French Pat. No. 2,347,170 a mixture of components able toform a polyurethane layer having energy-absorbing properties. For thispurpose, the polyol component is previously prepared by mixing apolytetramethylene glycol with a molecular mass of 1000 (for example,the product marketed under the name Polymeg 1000 by the Quaker OatsCompany), with 1,4-butanediol, the proportions of the two constituentsbeing such that the polytetramethylene glycol contributes 0.37equivalent in hydroxyl groups while the 1,4-butanediol contributes 0.63.To the polyol component is incorporated a stabilizer at a rate of 0.5%by weight of the total mass of the polyol component and of theisocyanate component, a spreading agent at a rate of 0.05% by weightcalculated in the same way and a catalyst, namely, dibutyltin dilaurateat a rate of 0.02% by weight calculated in the same way as above.

The isocyanate component used is3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI) exhibitingurea functions obtained by partial hydrolysis of the IPDI and having anNCO group content of about 31.5% by weight.

The components are taken in such amounts that the NCO/OH ratio is about1.

After degassing of the components under vacuum, the mixture, brought toabout 40° C., is poured on the polyurethane layer previously formed.Thus a layer about 0.55 mm thick is formed which in compartment 33 issubjected to a polymerization cycle consisting in 25 minutes of heatingat 120° C. at least.

The two-layer sheet is removed from the glass support and can easily behandled, stored or used immediately after for production of laminatedglasses.

To produce a glass, the previously obtained two layer glass is assembledwith an annealed glass sheet 2.6 mm thick. The glass can optionally behardened or tempered. Assembly can be performed in two stages, a firststage consisting in a preliminary assembly obtained by passage of theconstitutive elements of the glass between two rolls of a calender; forthis purpose; it is possible to use, for example, the device describedin the publication of European Pat. No. 0,015,209, the EA layer beingapplied against the inside face of the glass, and a second stageconsisting in putting the resulting laminated product in an autoclavewhere it is subjected to a pressure of about 10 bar at a temperature ofabout 135° C. for about an hour. This autoclave cycle can optionally bereplaced by an afterbake cycle without pressure.

The resulting glass exhibits an excellent optical quality and a perfecttransparency and a set of mechanical properties that enable it to beused as a vehicle windshield.

The adherence obtained between the glass sheet and the layer havingenergy-absorbing properties is measured on the produced glass by thepeeling tests described below.

A strip of the two-layer covering sheet 5 cm wide is cut out. The end ofthe strip on which a traction perpendicular to the surface of the glassis performed, with a traction speed of 5 cm per minute, is loosened. Theoperation is performed at 20° C. The average traction force necessary tomake the strip come loose is noted. By operating in this way, a tractionforce of 10 daN/5 cm is obtained.

Impact resistance tests were made at different temperatures on the glassproduced according to the example. The first impact resistance test wasmade with a steel ball weighing 2.260 kg (large ball test) which wasmade to fall on the central part of laminated glass sample 30.5 cmsquare, on a rigid frame. The approximate height was determined forwhich 90% of the samples tested at the selected temperature resisted theball drop without the ball going through them.

For the laminated glass according to the example the value obtained was9 meters.

Another impact resistance test was made with a steel ball of 0.227 kgand 38 mm in diameter. The test was made at a temperature of -20° C.,another test was made at +40° C. The values obtained were 11 and 13meters respectively.

Considering European standard R 43 in force, the desired results are atleast 4 meters with the large ball, at least 8.5 meters with the smallball at -20° C. and at least 9 meters with the small ball at +40° C.

Further, the thin IP layer shows sufficient surface properties for usein a laminated glass and particularly a resistance to scoring andabrasion measured as described below:

Resistance to scoring is measured by the scoring test known under thename "Mar resistant test" which is performed with the Erichsen type 413apparatus. A measurement is made of the charge to be carried on adiamond head to introduce a sustained scoring on the plastic layerassembled with the glass support. The charge should be greater than 20grams for the plastic layer to have the property of being self-healing.

Resistance to abrasion is measured per European standard R 43. For thispurpose, an assembled glass sample is made to undergo abrasion by anabrasive grinding wheel. After 100 abrasion revolutions, the blurdifference between the abraded part and unabraded part is measured by aspectrometer. The blur deviation (blur) should be less than 4% for thelayer to have antiabrasive quality. The blur difference here is 3.5%.

The glass according to the example exhibits all the characteristics thatmake it suitable for use as a vehicle windshield.

EXAMPLE 3

A two-layer sheet is formed, i.e., a layer 0.4 mm thick exhibiting self-healing and antilaceration properties and a layer 50 μm thick exhibitingadhesion properties.

For this purpose, the operation is opposite to that described in example2. The reaction mixture described in example 1 is cast with a castinghead, and after polymerization of this layer, the reaction mixture withwhich the EA layer in example 2 was formed is sprayed on it. Afterpolymerization, an adhesive layer is obtained.

The two-layer sheet is assembled with a laminated glass consisting oftwo sheets of glass and a polyvinylbutyral insert layer, the adhesivelayer being placed in contact with the inside sheet, so that the unitcan be used as a safety windshield exhibiting, among others,self-healing and antilaceration properties.

EXAMPLE 4

A sheet is produced having antishattering properties, which can be usedin vehicle or building glasses.

For this purpose, there is formed on a plane glass support a first layer100 μm thick by centrifugal spraying of a reaction mixture as describedin example 1.

After polymerization, a second layer 100 μm thick is formed on the firstlayer still placed on the plane support, by centrifugal spraying of thereaction mixture able to form an EA layer as described in example 2.

After polymerization of this second layer, the composite sheet isremoved from the forming support and is assembled, for example, with atempered glass sheet, the glass formed being used as a side glass formotor vehicles.

The two-layer sheet can also be assembled with a tempered or untemperedglass sheet and the unit used as a building glass. In case the glassbreaks, the plastic sheet holds the glass slivers.

EXAMPLE 5

The operation is the same as in example 4, but to form two layers, eachwith a thickness of 200 μm. The resulting sheet can be used as anantilacerating and selfhealing glass by being associated with alaminated glass consisting of two glass sheets and a polyvinylbutyralinsert.

EXAMPLE 6

An EA layer 0.4 mm thick is formed by reactive casting of the reactionmixture described in example 2 on an ethylene glycol polyterephthalateribbon 50 mm thick which is stretched as indicated in the devicedescribed in the publication of European Pat. No. 0,038,760. Afterpolymerization, the composite film is turned over and a layer 50 μmthick is formed on it, while it is stretched in the same way, bycentrifugal spraying of the reaction mixture described in example 1.

After polymerization, the resulting composite sheet can be assembledwith a one-piece glass support to constitute a safety glass that can beused as a motor vehicle windshield.

EXAMPLE 7

The reaction mixture described in example 2 is casted on a horizontalmetal strip as described for example in the publication of European Pat.No. 0,133,112, previously coated with a separation agent, to form an EAlayer 0.6 mm thick. After polymerization, the layer is detached from thesupport, turned over, and a second layer 50 μm thick is formed on itsface that was initially in contact with the support by centrifugalspraying of the reaction mixture described in example 1.

After separation from the metal forming support, the resulting sheet canbe used by associating it with a single-piece glass support to form asafety glass such as a motor vehicle windshield.

Having now fully described the present invention, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made thereto without departing from the spirit or scope of theinvention as set forth herein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A process for the continuous production of aplastic sheet of high optical qualtiy capable of being used in laminatedglasses, having a first thin layer resistant to scoring abrasion, and asecond layer formed thereon having energy-absorbing properties, whichcomprises:(a) high-speed centrifugal spraying a mixture of reactioncomponents from a bowl spray head, which components have been separatelyadded thereto, onto a plane horizontal support which is carried in auniform movement of advancement relative to the spraying, in order toform said first layer, and wherein the centrifugal spraying is performedwith said bowl spray head revolving at a speed between 1,000 and 80,000rpm and further wherein mixing of the reaction components is effecteddirectly in the spray head, and (b) forming on said first layer, saidsecond layer by reactive casting.
 2. The process as in claim 1, whereinthe mixture of reaction components in the bowl spray head comprisereaction components having different viscosities.
 3. The process asclaimed in claim 1, wherein said thin layer resistant to scoring andabrasion has a thickness of 50-200 μm.
 4. The process as in claim 1,wherein the high-speed centrifugal spraying of the mixture of reactioncomponents is performed on a first plastic layer already formed on theplane support.
 5. The process as in claim 4, wherein the already formedlayer is obtained by reactive casting of a mixture of reactioncomponents capable of forming a layer having energy-absorbingproperties.
 6. The process as in claim 1, wherein the layer havingenergy-absorbing properties is obtained by reactive casting of areaction mixture of an isocyanate component and a component with activehydrogens.
 7. The process as in claim 6, wherein the component withactive hydrogens is a polyol component.
 8. The process as in claim 1,wherein a reaction mixture capable of forming a polyurethane layer issprayed.
 9. The process as in claim 10, wherein the polyurethane layeris thermosetting polyurethane layer.
 10. The process as in claim 1,wherein a reaction mixture capable of forming a polyurethane layerhaving energy-absorbing properties is sprayed.
 11. The process as inclaim 1, wherein the sprayed reaction mixture contains a spreadingagent.
 12. The process as in claim 1, wherein the centrifugal sprayingis electrostatic.
 13. The process as in claim 1, wherein the planesupport on which the centrifugal spraying is performed is a flexiblestretched support going into the composition of the plastic sheet. 14.The process as in claim 13, wherein the flexible stretched support ismade of poly(ethylene glycol terephthalate).
 15. The process as in claim1, wherein said support is pre-heated before spraying said support withthe mixture of reaction components.
 16. The process as in claim 15,wherein said support is pre-heated to about 25°-60° C. before sprayingthe support with a thermosetting polyurethane.
 17. The process as inclaim 1, wherein said support is pre-heated with a separation agentbefore spraying the support with the mixture of reaction components.